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Correlations between Climate and Physiological Variables of Horses Reared in the Eastern Amazon

Letícia G. Athaíde ; Jamile Andréa Rodrigues da Silva ; Jose de Brito ; Lucieta Guerreiro Martorano ; Messy Hannear de Andrade Pantoja ; Yan Carlos Caldas Cruz ; Waléria Cristina Lopes Joset
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Some of the most stressful factors for horses are transportation, exercise, and changes in environmental temperature and humidity. Thus, this research aimed to verify the correlations between the climate variables in Ananindeua, Par?, Brazil on the physiological variables and adaptability indices of horses reared in the Eastern Amazon. The experiment was carried out at the Equestrian Center (latitude 1?23'33.4" S and longitude 48?24'27.6" W) in Ananindeua, Par?, Brazil. 12 clinically healthy male horses were used, eight of which of the Brazilian Sport Horse (BSH) breed and six of undefined breed (UB), at 12?3 years old and with mean weight of 483.8 kg. Data on the climate variables air temperature (AT), relative air humidity (RH), and black globe temperature (BGT) and on the physiological variables rectal temperature (RT), respiratory rate (RR), and body surface temperature (BST) were recorded. The environmental and physiological variables were read in the morning between 8 and 9 AM, while the animals remained in their individual bays, and between 2 and 3 PM, when the animals went to the pens. The data were used to calculate the temperature and humidity index (THI), globe temperature and humidity index (GTHI), and Benezra's thermal comfort index (BTCI). The analyses were done using the statistical software SYSTAT version 12. Pearson's linear correlations were carried out to verify the magnitude and direction of the proportionality of the different physiological variables, while the independence of the variances of the observation pairs used was verified. A strongly significant positive correlation (P<0.01) was found among all physiological variables and BTCI with AT, THI, and GTHI, while a negative correlation was found with RH. These results indicate that the values of these physiological values and BTCI tend to increase with AT, THI, and GTHI and to decrease with RH. It is concluded that, RT, RR, and BST are good indicators of the adaptability of horses reared under the climate conditions of the Eastern Amazon.